Laminate film

ABSTRACT

The object of the present invention is to provide a laminated film excellent in light resistance, scratch resistance, transparency, dimensional stability and adhesion to a hard coating layer. The present invention is a laminated film comprising a base material layer, an easily adhering layer and a hard coating layer, wherein the easily adhering layer is formed on the base material layer and the hard coating layer is formed on the easily adhering layer, and further wherein (1) the base material layer is formed of a polyester resin formed from naphthalenedicarboxylic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component, (2) the hard coating layer has an ultraviolet absorbing function and has a pencil hardness of H or higher on the hard coating layer surface, and (3) said laminated film has a variation (Δb*) of less than 2.0 between transmittance b* values obtained before and after a 300 hours&#39; xenon arc test of said laminated film.

TECHNICAL FIELD

The present invention relates to a laminated film comprising a basematerial layer, an easily adhering layer and a hard coating layer. Morespecifically, it relates to a laminated layer excellent in lightresistance, scratch resistance, transparency, dimensional stability andadhesion to the hard coating layer.

TECHNICAL BACKGROUND

Polyester films, particularly, biaxially oriented films formed ofpolyethylene terephthalate or polyethylene naphthalate have excellentmechanical properties, heat resistance and chemical resistance. They aretherefore widely used as materials for a magnetic tape, a ferromagneticthin tape, a photographic film, a packaging film, a film for electronicparts, an electrically insulating film, a film for metal laminates, afilm to be attached to the surface of a display, etc., a film forprotection of various parts, and the like.

In recent years, polyester films are used as films particularly forvarious optical devices, and they are used in the fields of a prism lenssheet that is a member of a liquid crystal display, a base film for atouch panel, a backlight, etc., a base film for anti-reflection, anelectromagnetic shield film for a plasma display, a base film for anorganic EL display, an anti-exposure base film for a display, and thelike. Base films for such optical films are required to have excellenttransparency and light resistance. However, polyester films aredeteriorated by ultraviolet light to cause changes in physicalproperties, such as discoloration, a decrease in mechanical strength,and the like. In the use thereof for a display, discoloration caused bylight deterioration impairs the color balance of the display, so thatthere has been a problem that a film having poor light resistance cannotbe used.

As means of improving polyester films in light resistance, there havebeen hitherto known a polyester film having an ultraviolet absorbentkneaded thereinto (Patent Document 1), a laminated film formed by mixingan ultraviolet absorbent with an acrylic resin, coating the mixture on apolyester film surface and drying the thus-formed coating (PatentDocument 2), a film formed by adjusting the refractive index and densityof a polyethylene naphthalate film to specific ranges (Patent Document3), a film formed by stacking two layers consisting of a resin layerformed of a benzotriazole-based-monomer-copolymerized acrylic resin anda surface-hardening layer having a pencil hardness of H or higher on athermoplastic film (Patent Document 4), and the like.

(Patent Document 1) JP-B-57-6470

(Patent Document 2) JP-B-H4-2101

(Patent Document 3) JP-B-53-40627

(Patent Document 4) JP-A-H9-234839

DISCLOSURE OF THE INVENTION

However, conventional polyester films have the following defects. Thatis, although the film having an ultraviolet absorbent kneaded thereintohas an effect against the deterioration of a polyester film in strengthand elongation, the film has a defect that since deterioration proceedson the film surface, the film is degraded in haze and transparency.

Further, the laminated film formed by mixing an ultraviolet absorbentwith an acrylic resin, coating the mixture on a polyester film surfaceand drying the thus-formed coating has a defect that it cannot maintainlight resistance required for use in a display since such films varydepending upon dispersibility of the ultraviolet absorbent contained.

While the film using a polyethylene naphthalate having a refractiveindex and a density in specific ranges produces effects to some extent,it cannot have light resistance satisfying demands.

The film formed by stacking two layers consisting of a resin layerformed of a benzotriazole-based-monomer-copolymerized acrylic resin anda surface-hardening layer having a pencil hardness of H or higher on athermoplastic film is excellent in scratch resistance. However, itsconstitution is complicated, and the adhesion to the hard coating layeris sometimes poor.

When a polyethylene terephthalate film (to be sometimes referred to as“PET film”) and a polyethylene naphthalene dicarboxylate film (PEN film)as films for use as base material layers are compared, the PET film isexcellent over the PEN film in light resistance, but it is sometimes notsufficient in dimensional stability. The PET film is therefore liable toshrink due to heat treatment in the process of producing a display, andsometimes involves a dimensional stability problem.

On the other hand, the PEN film is excellent over the PET film indimensional stability and excellent over the PET film as a base materialfor a display as described above, but the defect thereof is that it ispoor in light resistance.

It is an object of the present invention to overcome the above problemsand to provide a laminated film excellent in light resistance(weathering resistance), scratch resistance, transparency, dimensionalstability and adhesion to a hard coating layer.

According to the present invention, there is provided a laminated filmcomprising a base material layer, an easily adhering layer and a hardcoating layer, wherein the easily adhering layer is formed on the basematerial layer and the hard coating layer is formed on the easilyadhering layer, and further wherein

(1) the base material layer is formed of a polyester resin formed fromnaphthalenedicarboxylic acid as a main dicarboxylic acid component andethylene glycol as a main glycol component,

(2) the hard coating layer has an ultraviolet absorbing function and hasa pencil hardness of H or higher on the hard coating layer surface, and

(3) said laminated film has a variation (Δb*) of less than 2.0 betweentransmittance b* values obtained before and after a 300 hours' xenon arctest of said laminated film.

That is, the present invention has a characteristic feature in that by ahard coating layer having a specific ultraviolet absorbing functionovercomes the defect of a PEN film concerning light resistance while theexcellent transparency and dimensional stability of the PEN film ismaintained.

Further, the present invention has a characteristic feature in that thehard coating layer is improved in adhesion by providing an easilyadhering layer between the base material layer and the hard coatinglayer.

Further, the present invention has a characteristic feature in that thescratch resistance is improved by means of the hard coating layer havinga specific pencil hardness.

The laminated film of the present invention has a variation (Δb*) ofless than 2.0 in transmittance b* values, so that it can prevent a colorimbalance caused in the field of a display, and the like. The abovevariation in the transmittance b* values are evaluated by a method to bedescribed later.

BEST MODES OF THE INVENTION

<Base Material Layer>

In the present invention, the polyester resin constituting the basematerial layer is a polyester formed from naphthalenedicarboxylic acidas a main dicarboxylic acid component and ethylene glycol as a mainglycol component. The above “main” means that a component occupies atleast 90 mol %, preferably at least 95%, based on each constitutingcomponent.

Examples of the naphthalenedicarboxylic acid include2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and1,5-naphthalenedicarboxylic acid, and of these,2,6-naphthalenedicarboxylic acid is preferred.

When the polyester is a copolymer, a compound having a moleculecontaining two ester-forming functional groups can be used as acomonomer for constituting the copolymer. Examples of the dicarboxylicacid component for the copolymerization include oxalic acid, adipicacid, phthalic acid, sebacic acid, dodecanedicarboxylic acid,isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid,4,4′-diphenyldicarboxylic acid, phenylindanedicarboxylic acid,2,7-naphthalenedicarboxylic acid, tetralindicarboxylic acid,decalindicarboxylic acid and diphenyl ether dicarboxylic acid. As ahydroxycarboxylic acid, further, there are also includedhydroxycarboxylic acids such as p-hydroxybenzoic acid andp-hydroxyethoxybenzoic acid.

The glycol component for the copolymerization includes propylenedihydric alcohols such as propylene glycol, trimethylene glycol,tetramethylene glycol, hexamethylene glycol, cyclohexanemethyleneglycol, neopentyl glycol, an ethylene oxide adduct of bisphenol sulfone,an ethylene oxide adduct of bisphenol A, diethylene glycol andpolyethylene oxide glycol.

These compounds may be used singly, or two or more compounds of them maybe used. Of these, as a dicarboxylic acid component, isophthalic acid,terephthalic acid, 4,4′-diphenyldicarboxylic acid,2,7-naphthalenedicarbxoylic acid and p-hydroxybenzoic acid arepreferred. As a glycol component, trimethylene glycol, hexamethyleneglycol, neopentyl glycol and an ethylene oxide adduct ofbisphenolsulfone are preferred.

Further, the polyethylene-2,6-naphthalenedicarboxylate may be a compoundhaving some or all of its terminal hydroxyl groups and/or carboxylgroups blocked with a monofunctional compound such as benzoic acid,methoxypolyalkylene glycol, or the like, or it may be a compoundobtained by copolymerization that is carried out with a very smallamount of a trifunctional or higher ester-forming compound such asglycerin, pentaerythritol, or the like to such an extent that asubstantially linear polymer can be obtained.

The polyester resin for the base material layer can be produced by aconventionally known method. For example, there is a method in which alow-polymerization-degree polyester is obtained directly by a reactionbetween a dicarboxylic acid and a glycol. Further, it can be obtained bya method in which a lower alkyl ester of a dicarboxylic acid and aglycol are reacted in the presence of a conventionally knownester-exchange catalyst and then a polymerization reaction is carriedout in the presence of a polymerization catalyst.

Examples of the ester-exchange catalyst include compounds containingsodium, potassium, magnesium, calcium, zinc, strontium, titanium,zirconium, manganese and cobalt, and one or at least two members ofthese are used. The polymerization catalyst can be selected fromantimony compounds such as antimony trioxide and antimony pentoxide,germanium compounds typified by germanium dioxide, or titanium compoundssuch as tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate,partially hydrolysis products of these, titanylammonium oxalate,titanylpotassium oxalate and titanium trisacetyl acetonate.

When the polymerization is carried out after the ester-exchangereaction, generally, a phosphorus compound such as trimethyl phosphate,triethyl phosphate, tri-n-butyl phosphate, orthophosphoric acid, or thelike is added for deactivating the ester-exchange catalyst before thepolymerization. The content of phosphorus element in thepolyethylene-2,6-naphthalenedicarboxylate is preferably 20 to 100 weightppm from the viewpoint of thermal stability of the polyester. Inaddition, there may be employed a constitution in which the polyester isprepared into chips after melt polymerization and further polymerized ina solid phase under heat and reduced pressure or in the current of aninert gas such as nitrogen.

The polyester resin for the base material layer is preferably apolyester of which at least 90 mol % is formed of an ethylenenaphthalenedicarboxylate unit represented by —O—CH₂CH₂—O—CO-Q-C-(Qrepresents naphthalene-dily). Specifically, a polyester of which atleast 90 mol % is formed of an ethylene-2,6-naphthalenedicarboxylateunit is preferred, a polyester of which at least 95 mol % is formed ofan ethylene-2,6-naphthalenedicarboxylate unit is more preferred, and apolyester of which at least 97 mol % is formed of anethylene-2,6-naphthalenedicarboxylate unit is still more preferred.

The intrinsic viscosity of the polyester resin is preferably 0.40 dl/gor more, more preferably 0.40 to 0.9 dl/g. When the intrinsic viscosityis too low, the step is frequently discontinued in some cases. When theintrinsic viscosity is too high, the polyester resin has a high meltviscosity, so that its melt-extrusion is difficult. Further, thepolymerization takes a longer time, which is uneconomical and is notpreferred.

In the present invention, further, it is preferred in view of animprovement in light resistance to add an ultraviolet absorbent to thepolyester resin for constituting the base material layer. Particularly,the content of an ultraviolet-absorbing compound in the base material ispreferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight,since there can be prevented a decrease in light resistance caused bydeficiency of the ultraviolet-absorbing compound and the deteriorationof mechanical properties caused by a decrease in polymerization degreedue to an excess of the ultraviolet-absorbing compound.

Examples of the above ultraviolet absorbent preferably include knownultraviolet absorbents such as a salicylic-acid-containing compound, abenzophenone-containing compound, a benzotriazole-containing compound, acyclic-imino-ester-containing compound, and the like. Of these, abenzophenone-containing compound, a benzotriazole-containing compoundand a cyclic-imino-ester-containing compound are preferred. As acompound to be incorporated into the polyester, acyclic-imino-ester-containing compound is particularly preferred.

Examples of the benzophenone-containing compound preferably include2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, etc.,and examples of the above benzotriazole-containing compound preferablyinclude 2-(2′-hydroxy-5′-t-butylphenyl)benzotriazole, and the like.

As a cyclic-imino-ester compound, it is preferred to use at least onecompound selected from a cyclic imino ester of the following formula (I)or (II) in an unreacted form. These cyclic-imino-ester compounds arecompounds known as ultraviolet absorbents and are described, forexample, in JP-A-59-12952.

In the formula (I), X¹ is a divalent aromatic residue in which twobonding hands from X¹ shown in the above formula are on the 1-positionand the 2-position in positional relationship. n is 1, 2 or 3. R¹ is ahydrocarbon residue having a valence of n, and further, it may have aheteroatom. Otherwise, R¹ can be a direct bond when n=2.

In the formula (II), A is a group represented by the following formula(II-a) or a group represented by the following formula (II)-b. In theformula (II) and the formula (II)-a or (II)-b, R² and R³ are the sameas, or different from, each other, and are monovalent hydrocarbonresidues. X² is a tetravalent aromatic hydrocarbon residue, and it mayfurther contain a heteroatom.

Examples of X¹ preferably include 1,2-phenylene, 1,2-naphthylene,2,3-naphthylene and a group represented by the following formula (a) or(b). Of these, 1,2-phenylene is particularly preferred. In the formula(a) or the formula (b), R is —O—, —CO—, —S—, —SO₂—, —CH₂—, —(CH₂)— or—C(CH₃)₂—.

The aromatic hydrocarbon residues shown with regard to X¹ may besubstituted with alkyls having 1 to 10 carbon atoms such as methyl,ethyl, propyl, hexyl, decyl, etc.; aryls having 6 to 12 carbon atomssuch as phenyl, naphthyl, etc.; cycloalkyls having 5 to 12 carbon atomssuch as cyclopentyl, cyclohexyl, etc.; aralkyls having 8 to 20 carbonatoms such as phenylethyl, etc.; alkoxyls having 1 to 10 carbon atomssuch as methoxy, ethoxy, decyloxy, etc.; nitro; halogens such aschlorine, bromine, etc.; acyls having 2 to 10 carbon atoms such asacetyl, propionyl, benzoyl, decanoyl, etc.; and the like.

R¹ is a hydrocarbon residue having a valence of n (n is 1, 2 or 3), orit can be a direct bond only when n is 2.

(Case Where R¹ is a Monovalent Hydrocarbon Group)

Examples of the monovalent hydrocarbon residue (case when n=1) include,first, a non-substituted aliphatic group having 1 to 10 carbon atoms, anon-substituted aromatic group having 6 to 12 carbon atoms and anon-substituted alicyclic group having 5 to 12 carbon atoms.

Examples of the non-substituted aliphatic group having 1 to 10 carbonatoms include methyl, ethyl, propyl, hexyl, decyl, etc., examples of thenon-substituted aromatic group having 6 to 12 carbon atoms includephenyl, naphthyl, biphenyl, etc.; and examples of the non-substitutedalicyclic group having 5 to 12 carbon atoms include cyclopentyl,cyclohexyl, and the like.

Further, secondly, examples of the above monovalent hydrocarbon moietyinclude substituted aliphatic moieties or aromatic residues that can berepresented by the following formulae (c) to (f).

In the formulae, R⁴ is an alkylene group having 2 to 10 carbon atoms, aphenylene group or a naphthylene group. R⁵ is an alkyl having 1 to 10carbon atoms, phenyl or naphthyl. R⁶ is a hydrogen atom or any one ofgroups defined as R⁵. R⁷ is a hydrogen atom or any one of groups definedas R⁵.

Further, thirdly, the above monovalent hydrocarbon residue includes theabove non-substituted aromatic residues substituted, for example, withthe same substituents as those which are shown as substituents on thearomatic residue represented by the above X¹. Examples of thehydrocarbon residue that is substituted with such a substituenttherefore include tolyl, methylnaphthyl, nitrophenyl, nitronaphthyl,chlorophenyl, benzoylphenyl, acetylphenyl, acetylnaphthyl, and the like.

The monovalent hydrocarbon residue preferably includes groupsrepresented by the above formula (c), (d), (e) or (f), that is,substituted aliphatic residues or aromatic residues, and of these,substituted aromatic moieties are particularly preferred.

(Case Where R¹ is a Divalent Hydrocarbon Group)

Examples of the divalent hydrocarbon residue (case when n=2) include,first, a divalent non-substituted aliphatic group residue having 2 to 10carbon atoms, a divalent non-substituted aromatic group residue having 6to 12 carbon atoms and a divalent non-substituted alicyclic groupresidue having 5 to 12 carbon atoms.

Examples of the divalent non-substituted aliphatic groups having 2 to 10carbon atoms include ethylene, trimethylene, tetramethylene,decamethylene, etc., examples of the divalent non-substituted aromaticgroup having 6 to 12 carbon atoms include phenylene, naphthylene,P,P′-biphenylene, and examples of the divalent non-substituted alicyclicgroup having 5 to 12 carbon atoms include cyclopentylene, cyclohexylene,and the like.

Further, secondly, examples of the above divalent hydrocarbon groupresidue include a group represented by the following formula (g) and asubstituted aliphatic or aromatic group residue represented by thefollowing formula (h).

In the formulae, R⁸ is one of the groups defined with regard to R⁴. R⁹is one of the groups defined with regard to R⁴. R¹⁰ is one of the groupsdefined with regard to R⁶.

Further, thirdly, the above divalent hydrocarbon residue includes theabove divalent non-substituted aromatic group substituted, for example,with the same substituents as those which are shown as substituents onthe aromatic residue represented by the above X¹.

As R¹, when n is 2, of these, a direct bond or the above non-substitutedor substituted divalent aromatic hydrocarbon residues of the above firstto third classes are preferred, non-substituted or substituted aromatichydrocarbon residues of the first or third class in which two bondinghands are positioned on positions remotest from each other areparticularly preferred, and above all, p-phenylene, P,P′-biphenylene or2,6-naphthylene is preferred.

(Case Where R¹ is a Trivalent Hydrocarbon Group)

Examples of the trivalent hydrocarbon residue (case where n=3) includetrivalent aromatic group residues having 6 to 12 carbon atoms.

The above aromatic group residues include the following four groups.These aromatic group residues may be substituted with the samesubstituents as those that are shown as a substituent on the abovemonovalent aromatic group moieties.

The above R² and R³ are the same as, or different from, each other, andare monovalent hydrocarbon residues, and X² is a tetravalent aromatichydrocarbon residue. R² and R³ include, for example, the same groupsthat are shown with regard to R¹ when n=1 in the explanation of theabove formula (I). The tetravalent aromatic hydrocarbon residue includesthe following eight groups, in which R is as defined in the formula (a).These tetravalent aromatic hydrocarbon residues may be substituted withthe same substituents as those that are shown as a substituent on themonovalent aromatic group residue represented by R¹ in the explanationof the above formula (I).

Specific examples of the cyclic imino ester for use in the presentinvention, represented by the above formulae (I) and (II), include thefollowing compounds.

(Compound of the Above Formula (1), When n=1)

2-Methyl-3,1-benzooxazin-4-one, 2-butyl-3,1-benzooxazin-4-one,2-phenyl-3,1-benzooxazin-4-one, 2-(1- or2-naphthy)-3,1-benzooxazin-4-one, 2-(4-biphenyl)-3,1-benzooxazin-4-one,2-p-nitrophenyl-3,1-benzooxazin-4-one,2-m-nitrophenyl-3,1-benzooxazin-4-one,2-p-benzoylphenyl-3,1-benzooxazin-4-one,2-p-methoxyphenyl-3,1-benzooxazin-4-one,2-o-methoxyphenyl-3,1-benzooxazin-4-one,2-cyclohexyl-3,1-benzooxazin-4-one, 2-p- (orm-)phthalimidophenyl-3,1-benzooxazin-4-one,N-phenyl-4-(3,1-benzooxazin-4-one-2-yl)phthalimide,N-benzoyl-4-(3,1-benzooxazin-4-one-2-yl)aniline,N-benzoyl-N-methyl-4-(3,1-benzooxazin-4-one-2-yl)aniline,2-(p-(N-methylcarbonyl)phenyl)-3,1-benzooxazin-4-one.

(Compound of the Above Formula (I), When n=2)

2,2′-bis(3,1-benzooxazin-4-one),2,2′-ethylenebis(3,1-benzooxazin-4-one),2,2′-tetramethylenebis(3,1-benzooxazin-4-one),2,2′-decamethylenebis(3,1-benzooxazin-4-one),2,2′-p-phenylenebis(3,1-benzooxazin-4-one),2,2′-m-phenylenebis(3,1-benzooxazin-4-one),2,2′-(4,4′-diphenylene)bis(3,1-benzooxazin-4-one), 2,2′-(2,6- or1,5-naphthylene)bis(3,1-benzooxazin-4-one),2,2′-(2-methyl-p-phenylene)bis(3,1-benzooxazin-4-one),2,2′-(2-nitro-p-phenylene)bis(3,1-benzooxazin-4-one),2,2′-(2-chloro-p-phenylene)bis(3,1-benzooxazin-4-one),2,2′-(1,4-cyclohexylene)bis(3,1-benzooxazin-4-one),N-p-(3,1-benzooxazin-4-one-2-yl)phenyl,4-(3,1-benzooxazin-4-one-2-yl)phthalimide,N-p-(3,1-benzooxazin-4-one-2-yl)benzoyl,4-(3,1-benzooxazin-4-one-2-yl)aniline.

(Compound of the Above Formula (I), When n=3)

1,3,5-tri(3,1-benzooxazin-4-one-2-yl)benzene,1,3,5-tri(3,1-benzooxazin-4-one-2-yl)naphthalene,2,4,6-tri(3,1-benzooxazin-4-one-2-yl)naphthalene,

(Compound of the Above Formula (II))

2,8-dimethyl-4H,6H-benzo(1,2-d;5,4-d′)bis(1,3)-oxazin-4,6-dione,2,7-dimethyl-4H,9H-benzo(1,2-d;4,5-d′)bis(1,3)-oxazin-4,9-dione,2,8-diphenyl-4H,8H-benzo(1,2-d;5,4-d′)bis(1,3)-oxazin-4,6-dione,2,7-diphenyl-4H,9H-benzo(1,2-d;4,5-d′)bis(1,3)-oxazin-4,6-dione,6,6′-bis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-bis(2-ethyl-4H,3,1-benzooxazin-4-one),6,6′-bis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-methylenebis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-methylenebis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-ethylenebis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-ethylenebis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-butylenebis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-butylenebis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-oxybis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-oxybis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-sulfonylbis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-sulfonylbis(2-phenyl-4H,3,1-benzooxazin-4-one),6,6′-carbonylbis(2-methyl-4H,3,1-benzooxazin-4-one),6,6′-carbonylbis(2-phenyl-4H,3,1-benzooxazin-4-one),7,7′-methylenebis(2-methyl-4H,3,1-benzooxazin-4-one),7,7′-methylenebis(2-phenyl-4H,3,1-benzooxazin-4-one),7,7′-bis(2-methyl-4H,3,1-benzooxazin-4-one),7,7′-ethylenebis(2-methyl-4H,3,1-benzooxazin-4-one),7,7′-oxybis(2-methyl-4H,3,1-benzooxazin-4-one),7,7′-sulfonylbis(2-methyl-4H,3,1-benzooxazin-4-one),7,7′-carbonylbis(2-methyl-4H,3,1-benzooxazin-4-one),6,7′-bis(2-methyl-4H,3,1-benzooxazin-4-one),6,7′-bis(2-phenyl-4H,3,1-benzooxazin-4-one),6,7′-methylenebis(2-methyl-4H,3,1-benzooxazin-4-one),6,7′-methylenebis(2-phenyl-4H,3,1-benzooxazin-4-one).

Of the above compounds shown as examples, compounds of the above formula(I), more preferably, compounds of the above formula (I) in which n=2,particularly preferably, compounds of the following formula (I)-1 areadvantageously used. In the formula, R¹¹ is a divalent aromatichydrocarbon residue.

Of the compounds of the formula (I-1),2,2′-p-phenylenebis(3,1-benzooxazin-4-one),2,2′-(4,4′-diphenylene)bis(3,1-benzooxazin-4-one) and2,2′-(2,6-naphthylene)bis(3,1-benzooxazin-4-one) are particularlypreferred.

JP-A-59-12952 describes ultraviolet absorption properties of the abovecyclic imino ester, for example, with regard to its typical compounds,and such compounds are hence incorporated herein by reference thereto.

In the present invention, preferably, the base material layer containsno inert particles, or if contained, they have such a small diameter ora small content that they have no influence on properties.

The thickness of the base material layer is preferably 1 to 500 μm forattaining strength and certain free flexibility required when it is usedas a support for a liquid crystal, a hard coating, a touch panel,anti-dazzling treatment, an electromagnetic shielding film for PDP,organic EL, electron paper, solar cells, etc., or as a support in thefields of attachment to windows or automobiles. It is more preferably 12to 350 μm, particularly preferably 50 to 250 μm.

<Easily Adhering Layer>

In the laminated film of the present invention, the easily adheringlayer is formed on the base material layer. The easily adhering layer iscomprised of a polymer binder. The easily adhering layer may furthercontain inert particles, a wetting agent, an aliphatic wax and additiveparticles.

(Polymer Binder)

The polymer binder is comprised of a polyester resin. While the polymerbinder is preferably soluble or dispersible in water, there can be alsopreferably used a polymer binder that is soluble in water which containsan organic solvent to some extent.

As a polyester resin constituting the polymer binder, there can be useda polyester obtained from the following dicarboxylic acid component anddiol component.

That is, examples of the dicarboxylic acid component includeterephthalic acid, isophthalic acid, phthalic acid, anhydrous phthalicacid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylicacid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid,dimer acid and 5-sodiumsulfoisophthalic acid. As a polyester resin forconstituting the polymer binder, it is preferred to use a copolyesterobtained from two or more dicarboxylic acid components. The polyesterresin may contain an unsaturated polybasic component such as maleicacid, itaconic acid or the like or a hydroxycarboxylic acid componentsuch as p-hydroxybenzoic acid, or the like so long as the contentthereof is very small.

Examples of the diol component include ethylene glycol, 1,4-butanediol,diethylene glycol, dipropylene glycol, 1,6-hexanediol,1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, etc., andalso include poly(ethylene oxide) glycol and poly(tetramethylene oxide)glycol.

In the polyester resin constituting the polymer binder, the dicarboxylicacid component is preferably formed from 50 to 70 mol % of2,6-naphthalenedicarboxylic acid. As other dicarboxylic acid component,terephthalic acid or isophthalic acid is preferred. The diol componentis preferably formed from 80 to 95 mol % of ethylene glycol. As otherdiol component, diethylene glycol, or the like is preferred.

Therefore, the polyester resin constituting the polymer binder ispreferably a polyester obtained from 50 to 70 mol % of2,6-naphthalenedicarboxylic acid and 30 to 50 mol % of terephthalic acidor isophthalic acid for the dicarboxylic acid and from 80 to 95 mol % ofethylene glycol and 5 to 20 mol % of diethylene glycol for the diolcomponent.

The glass transition temperature of the polyester resin is preferably 40to 100° C., more preferably 60 to 80° C. Excellent adhesion andexcellent scratch resistance of the easily adhering layer itself can beattained so long as the glass transition temperature is in the aboverange. On the other hand, when the glass transition temperature is toolow, films are liable to cause a blocking, and when it is too high, thecoating film comes to be hard and fragile, so that the laminated film isundesirably degraded in scratch resistance.

The intrinsic viscosity of the polyester resin is preferably 0.41 dl/gor more, more preferably 0.40 to 0.9 dl/g. The polyester resin to beused for the easily adhering layer can be produced in the same manner asin the production of the polymer for the base material layer.

The thickness of the easily adhering layer is in the range of 0.01 to0.3 μm, preferably 0.02 to 0.25 μm. When the above thickness is toosmall, the adhesion strength is deficient. When it is too large, ablocking may take place or it may result in a large haze value.

(Inert Particles)

It is preferred to incorporate inert particles into the easily adheringlayer. The inert particles refer to organic or inorganic inertparticles, and examples of the inert particles include compositeinorganic particles of silica and titania, calcium carbonate, calciumoxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, crosslinkedacrylic resin particles, crosslinked polystyrene resin particles,melamine resin particles, crosslinked silicone resin particles, and thelike. Of these, crosslinked acrylic resin particles are preferred.

The inert particles preferably have an average particle diameter in therange of 40 to 120 nm. When the average particle diameter of the inertparticles is too large, particles are liable to drop off. When it is toosmall, sufficient lubricity or scratch resistance may not be obtained insome cases. The content of the inert particles in coating agent for theeasily adhering layer is preferably in the range of 0.1 to 10% byweight. When it is too small, no sufficient lubricity or scratchresistance can be obtained. When it is too large, undesirably, theeasily adhering layer is degraded in cohesion and is poor in theproperty of adhesion.

(Wetting Agent)

It is preferred to incorporate a wetting agent into the easily adheringlayer. The wetting agent includes anionic and nonionic surfactants suchas polyoxyethylene lauryl ether, polyoxyethylene alkylphenyl ether,polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerinfatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfonate,alkyl sulfosuccinate, and the like. The content of the wetting agent ispreferably 1 to 10% by weight. When the amount of the wetting agentadded is too small, no sufficient wettability to the polyester film isattained, and a coating agent is repelled. When it is too large,undesirably, the performance of the easily adhering layer is decreased.

(Aliphatic Wax)

It is preferred to incorporate an aliphatic wax into the easily adheringlayer. The aliphatic fax improves the laminated film more in filmsurface lubricity. The content of the aliphatic wax is preferably 0.5 to30% by weight, more preferably 1 to 10% by weight. When the abovecontent is too small, undesirably, the lubricity of the film surface maynot be obtained. When it is too large, undesirably, the adhesion to thepolyester film base material or the easy adherence to the hard coatingor an adhesive is sometimes insufficient.

Specific examples of the aliphatic wax include plant-origin waxes suchas carnauba wax, candelilla wax, rice wax, haze wax, jojoba oil, palmwax, rosin-modified wax, ouricury wax, sugarcane wax, esparto wax, barkwax, etc., animal-origin waxes such as beeswax, lanolin, spermaceti wax,insect wax, Shellac wax, etc., mineral-origin waxes such as montan wax,ozokerite, ceresin wax, etc., petroleum-origin waxes such as paraffinwax, microcrystalline wax, petrolatum, etc., and synthetichydrocarbon-origin waxes such as Fischer-Tropsch wax, polyethylene wax,polyethylene oxide wax, polypropylene wax, polypropylene oxide wax, andthe like. Of these, carnauba wax, paraffin wax and polyethylene wax areparticularly preferred in view of excellent in easy adhesion andlubricity to the hard coating or an adhesive. These are preferably usedin the form of a water dispersion since a load on the environment can bedecreased and since their handling is easy.

(Additive Particles)

For improvements in lubricity and scratch resistance, the easilyadhering layer may contain other additive particles to such an extentthat they do not influence transparency. Examples of the other additiveparticles include inorganic inert particles of each of calciumcarbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesiumoxide, sodium silicate, aluminum hydroxide, iron oxide, zirconium oxide,barium sulfate, tin oxide, antimony trioxide, carbon black, molybdenumdisulfate, etc., and particles of each of an acryl crosslinked polymer,a styrene crosslinked polymer, a silicone resin, a fluorine resin, abenzoguanamine resin, a phenolic resin, nylon resin, and the like. Foravoiding sedimentation in a water dispersion, it is preferred to selectparticles whose specific gravity does not exceed 3 among these when theparticles are formed of a solid substance insoluble in water.

The easily adhering layer for use in the present invention may containresins different from the above compositions or other compound differentfrom the above compounds, such as an antistatic agent, a colorant, acrosslinking agent, a ultraviolet absorbent, etc., as required forforming the coating layer.

(Solvent)

For forming a uniform easily adhering layer, the easily adhering layercomponent is applied onto the base material layer in a coating agentstate where the easily adhering layer component is dissolved ordispersed in a solvent. While water can be used as a solvent, watercontaining an organic solvent to some extent may be used. The abovesolvent is removed in the step of forming a film after the easilyadhering layer is formed, and it is preferably not contained in thefinal easily adhering layer.

<Method of Forming a Film>

In the laminated film of the present invention, the hard coating layercan be formed on the easily adhering layer by the following method aftera film having the easily adhering layer formed on the base materiallayer is produced.

That is, the polyester for constituting the base material layer ismelt-extruded in the form of a film and cooled to solidness with acasting drum to form an unstretched film. Then, the unstretched film isbiaxially stretched at a stretch ratio of 2.0 to 5.0 in the longitudinaland transverse directions at Tg to (Tg+60)° C. Further, the stretchedfilm is heat-set at a temperature of (Tm−100) to (Tm−5)° C. for 1 to 100seconds. The above Tg represents the glass transition temperature of thepolymer, and the above Tm represents the melting point of the polymer.

The stretching can be carried out by a generally employed method, suchas a method using a roll or a method using a stenter. The stretching maybe carried out simultaneously in the longitudinal and transversedirections; or may be carried out consecutively in the longitudinal andtransverse directions. When the simultaneous stretching is carried out,the easily adhering layer is coated on the biaxially oriented film. Whenthe consecutive stretching is carried out, preferably, the coating agentfor the easily adhering layer is coated on the monoaxially oriented filmthat has been stretched in one direction, the monoaxially oriented filmis stretched in the other direction as it is, and the film is heat-set.As a method of coating the easily adhering layer, a roll coating method,a gravure coating method, a roll brushing method, a spraying method, anair knife coating method, an impregnation method, a curtain coatingmethod, and the like can be employed singly or in combination.

When relaxation is carried out, it is effective to carry out heattreatment at a temperature of (X−80) to X° C. of the film. The above Xrepresents a heat-setting temperature. As a relaxation method, there isa method in which both edge portions of the film are detached somewherein a heat-setting zone before the film is taken up around a roll butafter its heat-setting, and the withdrawing rate relative to the filmfeed rate is decreased. Alternatively, there is a method in which thefilm is heated with an IR heater between two delivery rolls havingdifferent speeds. There is also a method in which the film is deliveredonto a heating and delivery roll and the rate of a delivery rollfollowing the heating and delivery roll is decreased. Further, there isanother method in which the take-up rate relative to the feed rate isdecreased while the film is delivered above a nozzle blowing hot airafter heat-setting. Alternatively, there is a method in which the filmis taken up with a film-forming machine, then, the film is deliveredonto a heating and delivery roll and the speed of a delivery roll isdecreased. Alternatively, there is another method in which, while thefilm is delivered through a heating oven or a heating zone using an IRheater, the speed of a roll provided after the heating zone is decreasedto be smaller than the speed of a roll provided before the heating zone.Any one of the above methods can be employed. Preferably, the decreaseratio of the speed on the take-up side is adjusted to 0.1 to 10% basedon the speed on the feed side to carry out the relaxation.

<Hard Coating Layer>

In the present invention, it is required to form a hard coating layerhaving the capability of absorbing ultraviolet on the easily adheringlayer for improving the film in light resistance. For such a hardcoating layer, there can be used a resin having the capability ofabsorbing ultraviolet as a material for forming the layer itself.

(Resin Having the Capability of Absorbing Ultraviolet)

As a resin having the capability of absorbing ultraviolet, anultraviolet-absorbing polymer obtained by copolymerizing an acrylicmonomer having benzophenone or benzotriazole as/on a side chain andother ethylenically unsaturated monomer is preferred.

The acrylic monomer having benzophenone as/on a side chain includesmonomers represented by the following formula.

wherein R is a hydrogen atom or methyl, and X is —O—, —OCH₂CH₂O— or—OCH₂CH(CH₃)O—.

Specifically, the above acrylic monomer having benzophenone includes2-hydroxy-4-acryloxybenzophenone,2-hydroxy-4-methacryloyloxybenzophenone,2-hydroxy-4-(2-acryloyloxy)ethoxybenzophenone,2-hydroxy-4-(2-methacryloyloxy)ethoxybenzophenone,2-hydroxy-4-(2-methyl-2-acryloyloxy)ethoxybenzophenone,2-hydroxy-4-(2-methyl-2-methacryloyloxy)ethoxybenzophenone, and thelike.

Of these, 2-hydroxy-4-acryloxybenzophenone or2-hydroxy-4-methacryloyloxybenzophenone is particularly preferred.

The acrylic monomer having benzotriazole as/on a side chain includesmonomers represented by the following formula.

wherein Y is a hydrogen atom, a halogen atom or methyl, R₁ is a hydrogenatom or a hydrocarbon group having 1 to 6 carbon atoms, R₂ is analkylene group having 1 to 6 carbon atoms and R₃ is a hydrogen atom ormethyl.

Specifically, the above acrylic monomer having benzotriazole includes2-[2′-hydroxy-5′-(methacryloyloxyethyl)phenyl]benzotriazole,2-[2′-hydroxy-5′-(acryloyloxyethyl)phenyl]benzotriazole,2-[2′-hydroxy-3′-t-butyl-5′-(methacryloyloxyethyl)phenyl]benzotriazole,2-[2′-hydroxy-3′-methyl-5′-(acryloyloxyethyl)phenyl]benzotriazole,2-[2′-hydroxy-5′-(methacryloyloxypropyl)phenyl]-5-chloro-benzotriazole,2-[2′-hydroxy-5′-(acryloyloxybutyl)phenyl]-5-methylbenzotriazole, andthe like.

Of these, 2-[2′-hydroxy-5′-(methacryloyloxyethyl)phenyl]benzotriazole or2-[2′-hydroxy-5′-(acryloyloxyethyl)phenyl]benzotriazole is particularlypreferred.

As other ethylenically unsaturated monomer, acrylic acid, methacrylicacid, alkyl ester of acrylic acid, alkyl ester of methacrylic acid,alkyl vinyl ether, alkyl vinyl ester, or the like is suitably used.

In the alkyl chain length of the alkyl ester of acrylic acid, alkylester of methacrylic acid and alkyl vinyl ether, and a carboxylic acidresidue in the alkyl vinyl ester, the number of carbon atoms ispreferably 1 to 8, more preferably 1 to 4.

The alkyl ester of acrylic acid includes methyl acrylate, ethylacrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc.,and the alkyl ester of methacrylic acid includes methyl methacrylate,ethyl methacrylate, propyl methacrylate, butyl methacrylate, and thelike.

The alkyl vinyl ether includes methyl vinyl ether, ethyl vinyl ether andbutyl vinyl ether. The alkyl vinyl ester includes vinyl formate, vinylacetate, vinyl acrylate, vinyl butyrate, vinyl crotonate, and the like.

Concerning the copolymerization ratio of the acrylic monomer havingbenzophenone or benzotriazole as/on a side chain and the otherethylenically unsaturated monomer, the ratio of the acrylic monomerhaving benzophenone or benzotriazole as/on a side chain is 10 to 70% byweight, preferably 20 to 65% by weight, and the ratio of the otherethylenically unsaturated monomer is 30 to 90% by weight, preferably 35to 80% by weight. When the ratio of the monomer having the ultravioletabsorbing function is less than the lower limit, the absorption startwavelength λs of the hard coating layer is shorter than the absorptionwavelength of the polyester resin of the base material layer, so thatthe ultraviolet absorption performance decreases. When the ratio of themonomer having the ultraviolet absorbing function exceeds the upperlimit, the hard coating layer is fragile, and no desired pencil hardnesscan be attained. The absorption start wavelength λs of the hard coatinglayer is preferably 385 to 390 nm.

The ultraviolet-absorbing polymer preferably has a weight averagemolecular weight of 5,000 to 1,000,000, more preferably 10,000 to800,000.

The coating agent to be used for forming the above hard coating layerpreferably contains 0.3 to 3 parts by weight, per 100 parts by weight ofthe resin component, of inert fine particles having a secondary particlediameter of 20 μm or less for the purpose of adjusting a gloss andimparting surface lubricity. When the above amount is less than 0.3 partby weight, there is produced a poor effect on an improvement inlubricity. On the other hand, when it exceeds 3 parts by weight, thepencil hardness of the hard coating layer obtained is sometimesdecreased.

Examples of the inert particles to be added to the coating agent includeinorganic particles such as silica, magnesium carbonate, aluminumhydroxide, barium sulfate, etc., and besides these, they includeparticles of an organic polymer such as polycarbonate, an acrylic resin,polyimide, polyamide, polyethylene naphthalate, a melamine resin, or thelike.

The coating method for forming the hard coating layer can be selectedfrom conventional methods that are known per se, such as roll coating,gravure coating, bar coating, extrusion coating and the like as requireddepending upon properties and coating amount of the coating agent.Although not specially limited, the thickness of the hard coating layeris preferably in the range of 1 to 15 μm. The concentration of a solidcontent in the coating agent is 30 to 70% by weight, and further, it ispreferably 40 to 60% by weight.

The hard coating layer is not specially limited in any point so long asit is formed on the easily adhering layer. There may be also employed aconstitution including a functional layer such as a gas barrier layer oran electrically conductive layer on the hard coating layer. In thelaminated film of the present invention, therefore, the hard coatinglayer (H), the base material layer (S) and the easily adhering layer (B)have a basic constitution of H/B/S or H/B/S/B/H. Further, when it has afunctional layer (F), the constitution is F/H/B/S, H/B/S/F, F/H/B/S/B/Hor H/B/S/B/H/F.

(Absorption Wavelength)

In the hard coating layer, preferably, the absorption wavelength λ ofthe polyester resin forming the base material layer and the absorptionstart wavelength λs of the hard coating layer satisfy the relationshipof λ≦λs≦400 nm. When λs is smaller than λ, undesirably, there isproduced no effect on the improvement in light resistance. Further, whenλs is greater than 400 nm, the film is colored, so that the film issometimes not usable in the field of displays. The above absorptionwavelength λ of the polyester resin refers to a wavelength at which thetransmittance measured with a spectrophotometer comes to be 20%.Further, the absorption start wavelength λs of the hard coating layerrefers to a wavelength at which the transmittance measured with aspectrophotometer comes to be 20% lower than the transmittance at 550nm.

When the base material layer contains an ultraviolet absorbent, theabsorption wavelength λ of the polyester resin of the base materiallayer and the absorption start wavelength λps of the ultravioletabsorbent contained in the base material layer satisfy λ<λps. The aboveabsorption start wavelength λps of the ultraviolet absorbent refers to awavelength at which the transmittance measured with a spectrophotometercomes to be 20% lower than the transmittance at 550 nm.

(Light Resistance)

In the laminated film of the present invention, the variation (Δb*)between transmittance b* values obtained before and after a 300 hours'xenon arc test of the laminated film is less than 2.0, preferably lessthan 1.0. When the transmittance b* value exceeds the upper limit, thefilm is colored in yellow, so that the film is sometimes not usable inthe field of displays.

(Pencil Hardness of Hard Coating Layer Surface)

In the laminated film of the present invention, preferably, the pencilhardness of the hard coating layer surface is H or higher. When theabove pencil hardness is H or lower, the laminated film is liable to bescratched and is not desirable in the field of displays. The abovepencil hardness is more preferably 2H or higher, still more preferably 3H or higher.

(Transparency)

In the laminated film of the present invention, preferably, the totallight transmittance in the visible light wavelength region is at least85%. When the total light transmittance is low, the laminated film isundesirable for use in an optical field due to a decrease in the sharpbrightness of a display screen, and the like. It is more preferably atleast 87%, still more preferably at least 90%. Further, the haze ispreferably less than 1%. When the haze is high, the visibility in thefield of displays is impaired, which is undesirable for use in anoptical field. It is more preferably less than 0.8%, still morepreferably less than 0.5%.

(Dimensional Stability)

The laminated film of the present invention preferably has a heatshrinkage factor, measured at 150° C. for 30 minutes, of less than 2%.When it is 2% or more, a laminated material undergoes cracking, orwrinkles are formed, when or after the functional layer is stacked onthe film, so that no sufficient functions may be exhibited due to thebreakage of the laminated material, and the like. It is more preferablyless than 1%, still more preferably less than 0.5%. The laminatedmaterial of the present invention may be treated at a high temperaturefor producing properties of the functional layer. When such a case istaken into account, it is preferred that the heat shrinkage factormeasured even at 200° C. for 10 minutes should be less than 2%. It ismore preferably less than 1%, still more preferably less than 0.5%.

EXAMPLES

Various property values and properties in the present invention weremeasured, and are defined, as follows.

(1) Film Thickness

A film was measured for a thickness at a stylus pressure of 30 g with anelectron micrometer (K-312A model, supplied by Anritsu K.K.).

(2) Haze, Total Light Transmittance

A 50 mm×50 mm sample piece was measured for a total light transmittanceTt (%) and a diffused light transmittance Td (%) with a haze meter,trade name “NDH2000” supplied by Nippon Denshoku Kogyo K.K., accordingto JIS K-7105, and a haze ((Td/Tt)×100) (%) was calculated and evaluatedon the basis of the following ratings.

Total light transmittance

◯ Total light transmittance is 85% or more . . . Excellent intransparency

Δ Total light transmittance is at least 80% but less than 85% . . .Transparency is poor to some extent.

× Total light transmittance is less than 80% . . . Poor transparency

Haze

◯ Haze is less than 1% . . . Excellent in transparency

Δ Haze is 1% or more but less than 1.5% . . . Transparency is poor tosome extent.

× Haze is 1.5% or more . . . Transparency is poor.

(3) Evaluation of Light Resistance

A film was subjected to an outdoor exposure acceleration test in a 65°C. and 50 RH % environment for an exposure time period of 300 hours witha xenon arc weatherometer (trade name “Suntest CPS”, model “CPS+”,supplied by Toyo Seiki Seisaku-sho, Ltd.) according to JIS-K-7350-2. Thetreated film was measured for a transmittance b* value based on L*a*b*color system with a color difference meter (SZ) supplied by NipponDenshoku Kogyo, to determine a post-treatment difference Δb*, and thefilm was evaluated on the basis of the following ratings.

⊚ Δb* value is less than 1.0 . . . Light resistance is remarkablyexcellent.

◯ Δb* value is 1.0 or more but less than 2.0 . . . Light resistance isexcellent.

Δ Δb* value is 2.0 or more but less than 4.0 . . . Light resistance ispoor to some extent.

× Δb* value is 4.0 or more . . . Light resistance is poor.

(4) Adhesion of Hard Coating Layer

A 5 μm thick hard coating layer was formed on an a coating surface of apolyester film and cross-cut in the form of a gridiron (100 squareshaving a size of 1 mm×1 mm each), and a 24 mm width scotch tape(supplied by Nichiban Co., Ltd.) was attached thereon. And, the tape wasrapidly peeled off along the attached tape direction and in a directionin parallel with the hard coating layer surface, and this operation wascarried out three times. A peeled surface was observed, and the resultwas evaluated on the basis of the following ratings.

◯ The area of a peeled surface is less than 20% . . . Adhesion strengthis remarkably excellent.

Δ The area of a peeled surface is 20% or more but less than 40% . . .Adhesion strength is poor to some extent.

× The area of a peeled surface is 40% or more . . . Adhesion strength isvery poor.

(5) Pencil Hardness

Pencils having various hardness values were pressed on a film layer atan angle of 90 degrees, the film was scratched with the pencils under aload of 1 kg, and pencil hardness was measured when scratches occurred,according to JIS K-5400. The pencil hardness on the hard coating layerside was evaluated on the basis of the following ratings.

⊚ Pencil hardness of 3H or higher . . . Scratch resistance is remarkablyexcellent.

◯ Pencil hardness of H or higher but lower than 3H . . . Scratchresistance is excellent.

× Pencil hardness of lower than H . . . Scratch resistance is poor.

(6) Dimensional Stability

A film sample was marked at an interval of 30 cm, heat-treated in anoven (200° C.×10 minutes) under no load, a distance between the markswas measured after the heat treatment, a heat shrinkage factor wascalculated on the basis of the following expression, and the film samplewas evaluated for dimensional stability on the basis of the followingratings.

Heat shrinkage factor (%)=(distance between marks before heattreatment−distance between marks after heat treatment)/distance betweenmarks before heat treatment×100

◯ Heat shrinkage factor is less than 2% . . . Dimensional stability isremarkable.

Δ Heat shrinkage factor is 2% or more but less than 4% . . . Dimensionalstability is normal.

× Heat shrinkage factor is 4% or more . . . Dimensional stability ispoor.

(7) Absorption Wavelength

For an absorption wavelength λ of a polyester resin, lighttransmittances in a wavelength region of 300 to 800 nm were continuouslymeasured with a double beam type spectrophotometer (trade name“UV-3100PC”, supplied by Shimadzu Corporation), and a wavelength atwhich the light transmittance came to be 20% was used as an absorptionwavelength λ.

For an absorption start wavelength λs of a hard coating layer, a filmwas formed on a glass and measured for a light transmittance in a regionof 300 to 800 nm with the above spectrophotometer, and a wavelength atwhich the light transmittance came to be lower than a lighttransmittance found at 550 nm by 20% was used as an absorption startwavelength.

Example 1

(Polyester for Base Material Layer)

An ester exchange reaction between 100 parts of dimethylnaphthalene-2,6-dicarboxylate and 60 parts of ethylene glycol wascarried out in the presence of 0.03 part of manganese acetatetetrahydrate as an ester exchange catalyst for 120 minutes while themixture was gradually temperature-increased from 150° C. to 238° C. Whenthe reaction temperature reaches 170° C. during the above process, 0.024part of antimony trioxide was added, and after completion of the esterexchange reaction, trimethyl phosphate (solution prepared byheat-treating it, under a pressure of 0.11 to 0.16 MPa in ethyleneglycol at 135° C. for 5 hours: 0.023 part as trimethyl phosphate) wasadded. Then, the reaction product was recharged into a polymerizer,temperature-increased up to 290° C. and allowed to undergo apolycondensation reaction under a high vacuum of 27 Pa or less, andafter completion of the polymerization, 1% by weight, per 99% by weightof a polymer, of an ultraviolet absorbent of the formula (A) was added,to give polyethylene-2,6-naphthalenedicarboxylate having an intrinsicviscosity of 0.61 dl/g and containing substantially no particles, as amaterial for forming a base material layer film.

(Easily Adhering Coating Agent)

A coating agent containing 85 parts by weight of a polyester, 5 parts byweight of inert particles and 10 parts by weight of a wetting agent wasdissolved in ion-exchange water to prepare a material for forming aneasily adhering layer. The above polyester (Tg=80° C.) used in thecoating agent was constituted from 2,6-naphthalenedicarboxylic acid 65mol %/isophthalic acid 30 mol %/5-sodiumsulfoisophthalic acid 5 mol % asan acid component and ethylene glycol 90 mol %/diethylene glycol 10 mol% as a glycol component. The inert particles were crosslinked acrylinert particles (average particle diameter 60 nm). The wetting agent waspolyoxyethylene (n=7) lauryl ether.

(Film Formation)

Pellets of the above polyethylene-2,6-naphthalenedicarboxylate weredried at 170° C. for 6 hours, fed to an extruder hopper and melted at amelting temperature of 305° C., and the melt was filtered with astainless steel wire filter having openings of 17 μm, extruded on arotary cooling drum having a surface temperature of 60° C. through a 3mm slit-shaped die, and rapidly cooled to give an unstretched film. Thethus-obtained unstretched film was pre-heated at 120° C. and stretched3.1 times longer in the longitudinal direction between low-speed andhigh-speed rolls under heat with a 900° C. IR heater 15 mm above thefilm. The above coating agent for forming an easily adhering layer wascoated on one surface of the above longitudinally stretched film with aroll coater such that a dry easily adhering layer had a thickness of 0.1μm.

Then, the film was supplied to a tenter and stretched 3.5 times wider inthe transverse direction at 145° C. The resultant biaxially orientedfilm was heat-set at a temperature of 240° C. for 40 seconds to give ahighly transparent polyester film having a thickness of 75 μm. An agent{circle around (1)} (trade name “ULS-1395LH” supplied by Ipposha OilIndustries Co., Ltd.) (the agent {circle around (1)} had been preparedby dissolving 30% by weight of2-[2′-hydroxy-5′-(methacryloyloxyethyl)phenyl]benzotriazole and 70% byweight of a methyl methacrylate monomer in a solvent mixture of toluenewith ethyl acetate, temperature-increasing the mixture up to 70° C. in areactor and carrying out a polymerization for 8 hours. The agent had asolid content of 30% by weight) was applied onto the easily adheringlayer side of the obtained film by a roll coating method for forming ahard coating layer, such that a dry layer had a thickness of 5 μm, andthe applied agent was dried at 100° C. for 2 minutes and aged at 23° C.for 2 days to form a hard coating layer.

The thus-obtained film was measured for properties, and Table 1 showsthe results. The obtained film was a film excellent in light resistance,scratch resistance, transparency, dimensional stability and adhesion tothe hard coating layer.

Example 2

A laminated polyester film was obtained in the same manner as in Example1 except that the polymer for forming a base material layer contained noultraviolet absorbent.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was inferior to the film of Example1 in light resistance, it was a film excellent in scratch resistance,transparency, dimensional stability and adhesion to a hard coatinglayer.

Examples 3 and 4

Laminated polyester films were obtained in the same manner as in Example1 except that the polymer for forming a base material layer contained noultraviolet absorbent and that the hard coating agent was replaced withagents (agent {circle around (2)} and agent {circle around (3)}) havingultraviolet-absorbing monomer contents shown in Table 1.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained films were inferior to the film ofExample 1 in light resistance, they were films excellent in scratchresistance, transparency, dimensional stability and adhesion to a hardcoating layer.

Comparative Example 1

(Polyester for Base Material Layer)

A reactor was charged with 96 parts of methyl terephthalate, 58 parts ofethylene glycol, 0.038 part of manganese acetate and 0.041 part ofantimony trioxide, and an ester exchange reaction was carried out withstirring until the temperature inside the reactor came to be 240° C.while methanol was distilled off. After completion of the ester exchangereaction, 0.097 part of trimethyl phosphate was added. Then, thereaction product was temperature-increased and, finally, apolycondensation was carried out under conditions of high vacuum and280° C., to give chips of polyethylene terephthalate having an intrinsicviscosity ([η]) of 0.64.

(Coating Agent for Easily Adhering Layer)

The same coating agent for an easily adhering layer as that used inExample 1 was used.

(Coating Agent for Hard Coating Layer)

The same coating agent as that used in Example 1 was used.

(Film Formation)

Then, the above chips of polyethylene terephthalate were dried at 170°C. for 3 hours, fed into a twin-screw extruder and melt-kneaded at 280°C., and the melt was rapidly cooled to solidness to obtain master chipsfor forming a base material layer film.

The above pellets of polyethylene terephthalate were dried at 160° C.for 3 hours, then, fed into an extruder hopper and melted at a meltingtemperature of 295° C., and the melt was rapidly cooled to solidness ona cooling drum maintained at 20° C., to give an unstretched film. Theunstretched film was stretched 3.5 times longer in the longitudinaldirection at 95° C., and the same coating agent for an easily adheringlayer as that used in Example 1 was applied such that a dry layer had athickness of 0.1 μm. The film was stretched 3.8 times wider in thetransverse direction at 110° C. and then heat-treated at 230° C., togive a biaxially oriented film having a thickness of 75 μm. A hardcoating layer was formed on the thus-obtained polyester film to give alaminated polyester film in the same manner as in Example 1.

The obtained film was measured for properties, and Table 1 shows theresults. While the obtained film was a film excellent in lightresistance, scratch resistance, transparency and adhesion to the hardcoating layer, it was inferior to the film of Example 1 in dimensionalstability.

Comparative Example 2

First, a film having a base material layer and an easily adhering layerwas obtained in the same manner as in Example 1 except that a polymerfor forming a base material layer contained no ultraviolet absorbent. Anacryl hard coating containing acryl-modified silica particles having noultraviolet-absorbing function (trade name “Z7501” supplied by JSRCorporation, agent {circle around (4)}, solvent: methyl ethyl ketone,solid content 50%) was coated thereon by a roll coating method such thata dry film had a thickness of 5 μm, and the applied agent was dried andirradiated with electron beam under conditions of 175 kV and 10 Mrad, toform a hard coating layer.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was a film excellent in scratchresistance, transparency, dimensional stability and adhesion to the hardcoating layer, it was very poor in light resistance.

Comparative Example 3

First, a base material layer film was obtained in the same manner as inExample 1 except that 0.25% by weight of spherical silica (averageparticle diameter 0.4 μm, refractive index 1.44) was added, as alubricant, to a polymer for forming a base material layer and that noeasily adhering layer was formed. A hard coating layer was formed on theabove film in the same manner as in Comparative Example 2, to obtain alaminated film.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was a film excellent in scratchresistance and dimensional stability, it was poor in transparency andvery poor in light resistance and adhesion to the hard coating layer.

Comparative Example 4

A laminated film was obtained in the same manner as in Example 1 exceptthat a polymer for forming a base material layer film contained noultraviolet absorbent and that the hard coating agent was replaced withan agent (agent {circle around (5)}) having an ultraviolet-absorbingmonomer content shown in Table 1.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was a film excellent in scratchresistance, transparency, dimensional stability and adhesion to a hardcoating layer, it was very poor in light resistance due to λs<λ.

Comparative Example 5

First, a film having a base material layer and an easily adhering layerwas obtained in the same manner as in Comparative Example 1. A hardcoating layer was formed on the film in the same manner as inComparative Example 2, to obtain a laminated film.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was a film excellent in scratchresistance, transparency and adhesion to a hard coating layer, it wasvery poor in light resistance and inferior in dimensional stability.

Comparative Example 6

A laminated film was obtained in the same manner as in Example 1 exceptthat a polymer for forming a base material layer film contained noultraviolet absorbent and that the hard coating agent was replaced withan agent (agent {circle around (6)}) having an ultraviolet-absorbingmonomer content shown in Table 1.

The thus-obtained film was measured for properties, and Table 1 showsthe results. While the obtained film was a film excellent in lightresistance, transparency, dimensional stability and adhesion to a hardcoating layer, it was very poor in scratch resistance. TABLE 1 ExampleComparative Example 1 2 3 4 1 2 3 4 5 6 Base Polyester PEN PET PEN PETPEN material Absorption 382 320 382 320 382 layer wavelength λ(nm)Lubricant No Yes No Ultraviolet Yes No Yes No absorbent Easily EasilyYes No Yes adhering adhering layer layer Hard Hard coating Agent {circlearound (1)} Agent {circle around (2)} Agent {circle around (3)} Agent{circle around (1)} Agent {circle around (4)} Agent {circle around (5)}Agent {circle around (4)} Agent {circle around (6)} coating agent layerUltraviolet Yes No Yes No Yes absorptivity Absorption 387 385 390 387 —— 375 — 395 start wavelength λs(nm) Ultraviolet-  30  20  50  30 — —  5—  80 absorbing monomer content (wt %) Properties Variation ⊚ ◯ ◯ ◯ ⊚ XX X Δ ◯ evaluated of b* value Pencil ◯ ◯ ◯ ◯ ◯ ⊚ ⊚ ⊚ ⊚ X hardness Haze ◯◯ ◯ ◯ ◯ ◯ X ◯ ◯ ◯ Total light ◯ ◯ ◯ ◯ ◯ ◯ Δ ◯ ◯ ◯ transmittanceDimensional ◯ ◯ ◯ ◯ Δ ◯ ◯ ◯ Δ ◯ stability Adhesion of ◯ ◯ ◯ ◯ ◯ ◯ X ◯ ◯◯ hard coating layer Comprehensive evaluation ⊚ ◯ ◯ ◯ Δ X X X X X

In Table, PEN represents polyethylene-2,6-naphthalenedicarboxylate, andPET represents polyethylene terephthalate.

EFFECT OF THE INVENTION

The laminated film of the present invention has excellent transparencyand has the following excellent properties. That is, in the laminatedfilm of the present invention, the hard coating layer has aultraviolet-absorbing function and has a Δb* value less than thepredetermined value, and the laminated film of the present invention isexcellent in light resistance. Further, since the hard coating layersurface has a pencil hardness of H or higher, the laminated film isexcellent in scratch resistance. Further, the polyester resin formedfrom naphthalenedicarboxylic acid as a main dicarboxylic acid componentand ethylene glycol as a main glycol component is used for the basematerial layer, so that the laminated film is excellent in dimensionalstability. Further, since the easily adhering layer is positionedbetween the base material layer and the hard coating layer, thelaminated film is excellent in adhesion to the hard coating layer.

INDUSTRIAL APPLICABILITY

The laminated film of the present invention is excellent in lightresistance, scratch resistance, transparency, dimensional stability andadhesion to a hard coating layer, so that the laminated film of thepresent invention can be used as a base film for a prism lens sheet, atouch panel, a backlight, etc., which are members of a liquid crystaldisplay, or as various optical films such as a base film for ananti-reflection film, an electromagnetic wave shielding film for aplasma display, a base film for an organic EL display, an anti-exposurebase film for a display, and the like.

1. A laminated film comprising a base material layer, an easily adheringlayer and a hard coating layer, wherein the easily adhering layer isformed on the base material layer and the hard coating layer is formedon the easily adhering layer, and further wherein (1) the base materiallayer is formed of a polyester resin formed from naphthalenedicarboxylicacid as a main dicarboxylic acid component and ethylene glycol as a mainglycol component, (2) the hard coating layer has an ultravioletabsorbing function and has a pencil hardness of H or higher on the hardcoating layer surface, and (3) said laminated film has a variation (Δb*)of less than 2.0 between transmittance b* values obtained before andafter a 300 hours' xenon arc test of said laminated film.
 2. Thelaminated film of claim 1, which satisfies the relational expression ofλ≦λs≦400 nm in which λ is an absorption wavelength of the polyesterresin of the base material layer and λs is an absorption startwavelength of the hard coating layer.
 3. The laminated film of claim 1or 2, which has a heat shrinkage factor of less than 2% in 200° C.×10minutes.
 4. The laminated film of any one of claims 1 to 3, which has atotal light transmittance of 85% or more in the visible light wavelengthregion.
 5. The laminated film of any one of claims 1 to 4, which has ahaze of less than 1%.
 6. The laminated film of any one of claims 1 to 5,wherein the polyester resin of the base material layer contains anultraviolet absorbent.
 7. The laminated film of any one of claims 1 to6, wherein the polyester resin of the base material layer is comprisedof at least 90 mol % of an ethylene-2,6-naphthalenedicarboxylate unit.8. The laminated film of any one of claims 1 to 7, wherein the easilyadhering layer is formed of a polyester resin having a glass transitiontemperature of 40 to 100° C.
 9. The laminated film of claim 8, whereinthe easily adhering layer is formed of a polyester resin obtained from50 to 70 mol % of 2,6-naphthalenedicarboxylic acid and 30 to 50 mol % ofterephthalic acid or isophthalic acid as a dicarboxylic acid componentand from 80 to 95 mol % of ethylene glycol and 5 to 20 mol % ofdiethylene glycol as a diol component.
 10. The laminated film of claim8, wherein the easily adhering layer contains inert particles.
 11. Thelaminated film of claim 1, wherein the hard coating layer is formed of acopolymer from an acrylic monomer having benzophenone or benzotriazoleon a side chain and other ethylenically unsaturated monomer.
 12. Thelaminated film of claim 11, wherein the acrylic monomer havingbenzophenone on a side chain is 2-hydroxy-4-acryloxybenzophenone or2-hydroxy-4-methacryloyloxybenzophenone.
 13. The laminated film of claim11, wherein the acrylic monomer having benzotriazole on a side chain is2-[2′-hydroxy-5′-(methacryloyloxyethyl)phenyl]benzotriazole or2-[2′-hydroxy-5′-(acryloyloxyethyl)phenyl]benzotriazole.
 14. Thelaminated film of claim 11, wherein the other ethylenically unsaturatedmonomer is at least one monomer selected from the group consisting ofacrylic acid, methacrylic acid, alkyl ester of acrylic acid and alkylester of methacrylic acid.
 15. The laminated film of claim 11, whereinthe hard coating layer is formed of a copolymer obtained bycopolymerization of 10 to 70% by weight of an acryl monomer havingbenzophenone or benzotriazole on a side chain and 30 to 90% by weight ofother ethylenically unsaturated monomer.